/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hedwig.server.common;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import com.google.protobuf.ByteString;

public class ByteStringInterner {
    // TODO: how to release references when strings are no longer used. weak
    // references?

    private static ConcurrentMap<ByteString, ByteString> map = new ConcurrentHashMap<ByteString, ByteString>();

    public static ByteString intern(ByteString in) {
        ByteString presentValueInMap = map.get(in);
        if (presentValueInMap != null) {
            return presentValueInMap;
        }

        presentValueInMap = map.putIfAbsent(in, in);
        if (presentValueInMap != null) {
            return presentValueInMap;
        }

        return in;

    }
}
